The invention relates to a method of executing an address-jump command in a stored-program sequential-control system for processing machines, and in particular for industrial sewing machines, and sequential-control circuitry for the practice of the method.
A method and circuit of this kind are described in ELEKTRONIK, 1975, No. 1, pp. 53 to 58, especially in section 2. With a view to keeping the cost of the program memory down, the described method and circuitry are limited to dual jumps and work with a parallel-loadable address counter for accessing of the program memory. If no jump command is provided between two program steps or a possible jump command is not present, the address counter is advanced to the next counter position which corresponds to the next address and thus leads to the reading of the next data block in the program memory. But if a jump command is present, that is to say, if the next data block stored in the program memory is not to become effective, then one bit of the binary count of the address counter is inverted and thus an entirely different address in the program memory is read instead of the normal, stepwise sequence of counter positions. From there on the stepwise progression of counter positions continues until another jump command brings about a change in the binary representation of the count, and accordingly a jump into still another section of the overall counting range. Such a program-memory structure which permits program jumps to be made in the course of sequential-control program execution is referred to as "paging". This greatly increases the amount of storage required, because such intervention in the binary-coded address leads to entirely different memory regions which from the standpoint of program size should not be needed in the first place. Storage capacity of such size is necessarily poorly utilized. On the other hand, if the occupation of the available memory locations is to be optimized, then very hard-to-follow storage of the program must be tolerated; resulting malfunctions due to inadvertent double occupancy of memory locations are hard to analyze and can be corrected only by costly intervention in memory-location assignment.